Definition - What does Winter Kill mean?
Winter kill refers to a plant dying because of the harsh effects of winter time weather. Usually prolonged cold weather does not damage a dormant plant as significantly as ongoing temperature fluctuations.
Plants acclimatize slowly to temperature changes as the weather becomes colder and colder. A sudden and unexpected hard freeze often significantly damages a plant if it has not had time to adjust to the cold weather. If the temperature drops below the plant’s threshold then it will sustain damage or perish, suffering a 'winter kill'.
MaximumYield explains Winter Kill
Winter kill is especially dangerous to plants in the spring. During the spring months, many plants start to break dormancy and develop buds and foliage. An unexpected spring frost can damage the flowers' new growth.
Even trees are susceptible to winter kill. When the temperature drops rapidly to below 15 degrees Fahrenheit, the tree’s bark starts to rapidly contract, which causes stress fissures. The cracks in a tree usually happen on the south side of the tree.
Winter winds also dry out the needles of evergreen trees. The roots of a plant can also sustain winter kill if the soil freezes. Snow usually helps insulate the soil but a sudden hard freeze after a rain shower can damage the roots.
There are a few things a gardener can do to lessen the chances of their plants experiencing a winter kill. This include hardening off seedlings before planting them in the spring, and adding ground cover and cloches to protect plants from brutal temperatures. If your climate is unpredictable, wait as long as possible to protect against winter kill.